1. Field of the Invention
The present invention relates generally to developing apparatus for use in electrophotographic recording machines, and more particularly to a developing apparatus using a developer of the two-component system.
2. Description of the Prior Art
One example of the developing apparatus of the type concerned is disclosed in Japanese Patent Publication No. 62-33583. The disclosed developing apparatus includes a bucket roller rotatably disposed in a development tank or housing and having a plurality of elongate buckets extending between respective peripheral surfaces of a pair of parallel spaced circular disks, a cylindrical tube disposed in the bucket roller and extending along an axis of rotation of the bucket roller, a developer inlet and a developer outlet formed at opposite ends of the cylindrical tube, developer guide members attached to the bucket roller for transporting a developer within the development housing from the developer outlet toward the developer inlet, and a conveyor means disposed in the cylindrical tube for transporting the developer from the developer inlet toward the developer outlet. The bucket roller and the transport means serve to transport the developer in the axial direction of the bucket roller while circulating the developer through the inside and the outside of the cylindrical tube, thereby mixing the developer within the bucket roller. The bucket roller supplies the developer onto a developing roller.
Another developing apparatus is disclosed in U.S. Pat. No. 4,033,294, which comprises a plurality of parallel juxtaposed developing rollers and a mixing and transporting roller disposed adjacent to an endmost one of the developing rollers. The mixing and transporting roller includes a plurality of spaced-apart auger elements mounted on a drive shaft and a plurality of radially extending flat bars mounted on the periphery of the auger elements. The mixing and transporting roller serves to mix a developer while feeding the same in the axial direction and to transport the developer toward the endmost developing roller.
In these known developing apparatus described above, since both the mixing of the developer and the feeding of the developer toward the developing roller are performed at one position or by a single component (by the bucket roller in Japanese Patent Publication No. 62-33583 and by the mixing and transporting roller in U.S. Pat. No. 4,033,294), a sufficient mixing of the developer is not always guaranteed.
Furthermore, in the production of the bucket roller which is used for agitating or stirring the developer, the pair of circular disks and the plural buckets are manufactured separately. After the circular disks and the buckets are assembled together, the plural developer guide members in the form of fins are attached to each bucket by means of screws, for example. In addition, the bucket roller is rotatably mounted on the cylindrical tube via a bush of a sintered metal slidably fitted over a fixed bearing mounted on the cylindrical tube. Thus, the conventional developing apparatus is composed of a relatively large number of structural components, complicated in construction, requires a tedious and time-consuming assembling work and is expensive to manufacture. Another drawback associated with the conventional developing apparatus is an unreliable detection of the density of the developer caused due to an abrasive wear on sliding surfaces of movable components or an improper positioning of a developer density sensor.